JP2018179974A - Optical measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lessen processing of a timer circuit without decreasing detection sensitivity.SOLUTION: A light reception array unit 3 comprises a plurality of optical detectors 31 outputting pulse signals by an incidence of photon. Light reception elements included in the plurality of optical detectors 31 are configured to form a single image as a whole. A plurality of measurement units 4 are provided for each of a plurality of light reception groups G1 to Gx dividing the light reception array unit 3. Each measurement unit 4 is configured to, according to the pulse signal output from the corresponding light reception group, generate time information Tp representing an elapsing time from an irradiation timing to be input from an outside, and light-amount information Cp expressing a quantity of the optical detectors 31 outputting the pulse signals. A histogram generation unit 52 is configured to, according to the time information Tp and light-amount information Cp measured in the plurality of measurement units 4, integrate values indicated by the light-amount information for each time expressed by the time information Tp.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a technology for determining the flight time of light.

  A photodetector is known that detects the light reception intensity by counting the number of pulse signals (hereinafter referred to as the number of responses) output from individual SPADs in which photons are incident, using a SPAD array in which a plurality of SPADs are arranged. There is. SPAD is an abbreviation of Single Photon Avalanche Diode. SPAD is an avalanche photodiode that operates in Geiger mode and can detect the incidence of single photons.

  In Patent Document 1, it is assumed that the reflected light is received when the number of responses detected by the light detector after irradiating light is equal to or greater than the trigger threshold, and the flight time of light from irradiation to light reception (hereinafter referred to as TOF) A technique is described which measures the distance from the measured TOF to an object that reflects light. TOF is an abbreviation of Time Of Flight. Also, in order to remove the influence of disturbance light etc. incident on the SPAD array, measurement of TOF is repeatedly performed to create a histogram in which the number of responses is integrated for each measurement time, and the time obtained from the maximum value of the histogram is generated , It has been used to calculate the distance.

JP, 2014-81254, A

However, as a result of detailed investigations by the inventor, the following problems have been found in the prior art described in Patent Document 1.
That is, in the prior art, when the number of SPADs included in the SPAD array is increased in order to improve detection performance, the number of responses in the light detector is increased. The processing load of the circuit is increased. If the processing load exceeds the processing capacity of the clock circuit, the detection performance will be reduced.

  On the other hand, it is conceivable to suppress the number of responses by suppressing the sensitivity of the SPAD. However, in this case, it is impossible to detect reflected light from a long distance with low intensity or reflected light from an object with a low reflectance.

  One aspect of the present disclosure is to provide a technology capable of reducing the processing of a timer circuit without reducing detection sensitivity.

A light detection device according to one aspect of the present disclosure includes a light receiving array unit (3, 3c), a plurality of measurement units (4, 4c), and a signal processing unit (5).
The light receiving array unit is configured such that a plurality of light detectors (31, 31c) that output pulse signals upon incidence of photons form a light receiving group, and a plurality of light receiving groups form one pixel, and such a pixel Have one or more

  The measuring unit is provided for each of the plurality of light receiving groups. The measuring unit receives time information indicating an elapsed time from the irradiation timing input from the outside according to the pulse signal output from the light receiving group, and the light amount acquired at one or more timings specified from the time information. Generate information. As the light amount information, the number of light detectors outputting pulse signals among the plurality of light detectors belonging to the light receiving unit loop is used.

The signal processing unit determines the flight time of light in accordance with at least one of time information and light amount information measured by a plurality of measurement units corresponding to one pixel.
According to such a configuration, it is possible to suppress the number of pulse signals to be processed by each measurement unit without reducing the sensitivity of the light detector.

  In addition, the reference numerals in parentheses described in this column and the claims indicate the correspondence with the specific means described in the embodiment described later as one aspect, and the technical scope of the present disclosure It is not limited.

It is a block diagram showing composition of a laser radar of a 1st embodiment. It is explanatory drawing which illustrates the content of separate memory. It is explanatory drawing regarding a histogram. FIG. 6 is a block diagram showing a configuration of a histogram generation unit 52. FIG. 7 is a state machine diagram for explaining the operation of the histogram generation unit 52. It is a block diagram which shows the structure of the laser radar of 2nd Embodiment. It is explanatory drawing which illustrates how to allocate a light reception group to a measurement part. It is a block diagram which shows the structure of the laser radar of 3rd Embodiment. It is explanatory drawing which illustrates the assignment method of the light reception group with respect to a histogram production | generation part. It is a circuit diagram which shows the structure of the photodetector in 1st-3rd embodiment. It is a block diagram which shows the structure of the laser radar of 4th Embodiment. It is a circuit diagram which shows the structure of the photodetector in 4th Embodiment. It is a block diagram which shows the structure of the modification of 2nd Embodiment. It is a block diagram which shows the structure of the modification of 3rd Embodiment.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.
[1. First embodiment]
[1-1. Constitution]
The laser radar 1 of the present embodiment is mounted on a vehicle, detects various objects present around the vehicle, and generates information about the objects. As shown in FIG. 1, the laser radar 1 includes an irradiation unit 2, a light reception array unit 3, a plurality of measurement units 4, a signal processing unit 5, and a histogram storage unit 6. The configuration obtained by removing the irradiation unit 2 from the laser radar 1 corresponds to an optical measurement device.

  The irradiation unit 2 repeatedly irradiates pulsed laser light at preset intervals and notifies the plurality of measurement units 4 of the irradiation timing. Hereinafter, a cycle of irradiating laser light is referred to as a measurement cycle.

  The light receiving array unit 3 has a plurality of light receiving groups G1 to Gx. x is an integer of 2 or more. Each light receiving group Gi includes Mi light detectors 31 respectively. i is any of the values from 1 to x. Each photodetector 31 comprises a SPAD.

  SPAD is an abbreviation of Single Photon Avalanche Diode. SPAD is an avalanche photodiode operating in Geiger mode which applies a voltage higher than the breakdown voltage as a reverse bias voltage, and can detect the incidence of a single photon. The light receiving array unit 3 includes a total of M1 + M2 +... + Mx SPADs. These SPADs are arranged to form a two-dimensional matrix to form a light receiving surface. Here, SPADs for a plurality of lines in the matrix of SPADs are allocated to the light receiving groups G1 to Gx.

  The light receiving circuit outputs a pulse signal P having a preset pulse width when photons are incident on the SPAD. In the following, each pulse signal output by the Mi light detectors 31 included in the light reception group Gi is represented by P1 to PMi.

  Each photodetector 31 includes, as shown in FIG. 10, an SPAD 81, a quench resistor 82, an inverting circuit 83, a D flip-flop circuit (hereinafter, DFF circuit) 84, and a delay circuit 85. SPAD 81 has its anode connected to the negative power supply and its cathode connected to the positive power supply via quench resistor 82. The quench resistor 82 applies a reverse bias voltage to the SPAD 81. Further, the quench resistance 82 stops Geiger discharge of the SPAD 81 by a voltage drop generated by the current flowing to the SPAD 81 when photons enter the SPAD 81 and the SPAD 81 breaks down. As the quench resistor 82, a resistive element having a predetermined resistance value, or a MOSFET or the like whose on-resistance can be set by a gate voltage is used.

  The inverting circuit 83 is connected to the cathode of the SPAD 81. When SPAD 81 is not broken down, the input of inverting circuit 83 is at high level. In the state where the SPAD 81 is broken down, the current flows through the quench resistor 82, whereby the input of the inverting circuit 83 changes to the low level. The DFF circuit 84 changes its output to high level at the rising edge where the output of the inverting circuit 83 changes from low level to high level. The output of the DFF circuit 84 is connected to the reset terminal of the DFF circuit 84 via the delay circuit 85. The delay circuit 85 inverts the signal level of the output of the DFF circuit 84 and delays the output by a predetermined delay time τ and inputs the result to the reset terminal. As a result, when the delay time τ elapses after the output of the DFF circuit 84 changes to the high level, the DFF circuit 84 is reset to change to the low level.

  The plurality of measurement units 4 have the same number x as the light reception groups G1 to Gx. Each measurement unit 4 is associated with any one of the light reception groups G1 to Gx on a one-to-one basis. The plurality of measurement units 4 are all configured in the same manner, and therefore, one measurement unit 4 associated with the light reception group Gi will be described below.

  Based on pulse signals P1 to PMi output in parallel from the light reception group Gi and the irradiation timing supplied from the irradiation unit 2, the measurement unit 4 performs TOF which is the flight time of light required from irradiation to light reception. The time information Tp to be represented and the light amount information Cp indicating the light amount at the time of light reception are generated. TOF is an abbreviation of Time Of Flight. The measurement unit 4 includes a trigger unit 41, a clock unit 42, a count unit 43, and a temporary storage unit 44.

  The trigger unit 41 has the number of pulse signals P1 to PMi simultaneously output from the light receiving group Gi, that is, the number of photodetectors 31 outputting pulse signals in response to photons is equal to or greater than the trigger threshold TH. In this case, the trigger signal TG having a predetermined pulse width representing the light reception timing is output. When the light receiving group Gi receives reflected waves from a plurality of objects located at different distances, the trigger unit 41 outputs a plurality of trigger signals TG. The trigger threshold TH may be a fixed value or may be a variable value that changes according to the situation.

  The timer unit 42 is a so-called TDC, measures the time from the irradiation timing notified from the irradiation unit 2 to the light reception timing indicated by the trigger signal TG, and outputs it as time information Tp. TDC is an abbreviation for Time to Digital Converter. The TDC is composed entirely of digital circuits.

  The counting unit 43 counts the number of responses Cx, which is the number of pulse signals P1 to PMi simultaneously output from the light receiving group Gi, at a timing according to the trigger signal TG, and subtracts the bias value Cb from the number of responses Cx. The adjustment response number, which is the result, is output as light amount information Cp representing the intensity of the received light. The timing according to the trigger signal TG may be the timing at which the trigger signal TG is output, or may be the timing after delaying this by a predetermined delay amount. Also, the bias value Cb may be a fixed value or a variable value that changes according to the situation. The bias value Cb may be 0 in the case of a fixed value. Further, in the case of a variable value, the bias value Cb may be set in conjunction with the trigger threshold TH, and is set according to either or both of the ambient brightness and the free space of the histogram storage unit 6 It may be done.

  The temporary storage unit 44 has a RAM, which is an arbitrarily readable / writable memory. In the temporary storage unit 44, as shown in FIG. 2, the light amount information Cp generated by the counting unit 43 is stored at an address associated with the time information Tp generated by the timer unit 42. The time information Tp is a value expressed in units of time domains (hereinafter, time bins) divided by the time resolution of the timer unit 42. Therefore, the larger the address, the longer the TOF, and hence the greater the distance to the object. The bit width of the data stored in temporary storage unit 44 may have a minimum size that can represent the number Mi of SPADs included in light reception group Gi.

  The histogram storage unit 6 has a RAM, which is an arbitrarily readable / writable memory. The address of the histogram storage unit 6 is associated with the time information Tp, as in the temporary storage unit 44, as shown in FIG. The bit width of the data stored in the histogram storage unit 6 is the expected value of the number of responses detected in one measurement, the integration number X, which is the number of times the signal processing unit 5 repeats the integration when generating the histogram, etc. Therefore, the integrated value is appropriately set so as not to overflow. The integration number X may be 1 or more.

The signal processing unit 5 includes an information generation unit 51 and a histogram generation unit 52.
The information generation unit 51 operates every X measurement cycles, that is, each time a histogram is generated, and generates information on an object that has reflected light based on the histogram generated by the histogram generation unit 52. Specifically, the maximum value of the histogram is extracted as luminance, and for each of the extracted maximum values, the time corresponding to the address at which the maximum value is obtained is specified. Furthermore, an object including the distance to each object causing the local maximum value to be generated on the histogram, the reliability of the object, and the like based on the combination of the extracted luminance and the time bin (that is, TOF) Generate information. The generated object information is provided to various in-vehicle devices using the object information via an in-vehicle LAN (not shown).

  The histogram generation unit 52 operates every measurement cycle, and updates the content of the histogram stored in the histogram storage unit 6 according to the information stored in each temporary storage unit 44 that each of the plurality of measurement units 4 has.

  The histogram generation unit 52 includes a comparison unit 521 and a memory control unit 522 as shown in FIG. The temporary storage unit 44 is configured to output the smallest address among the addresses to which data are written and the data stored in the address in the initial state. In addition, temporary storage unit 44 is configured to sequentially output the next smaller address among the addresses to which data are written and the data stored in the address according to update instruction acq from memory control unit 522. .

  The comparison unit 521 compares the inputs from the plurality of temporary storage units 44, selects the light reception group G outputting the smallest address, and selects the selected light reception group (hereinafter, selected group) SG and The memory control unit 522 is supplied with an address (hereinafter, selected address) SA and data (hereinafter, selected data) SD input from the temporary storage unit 44 of the group. When there are a plurality of light receiving groups G which issue the smallest address, among the plurality of light receiving groups G, only one having the smallest identifier for identifying the light receiving group is set as the selected group SG. Not limited to this, all of the plurality of light receiving groups may be set as selected groups SG1, SG2,. In this case, the selection data SD may be a total value of all data input from the selection groups SG1, SG2,.

  The memory control unit 522 updates the value of the histogram stored in the histogram storage unit 6 using the selection address SA and the selection data SD supplied from the comparison unit 521. Specifically, the data of the selected address SA is read from the histogram storage unit 6, the selected data SD is added to the read data, and the read data is written in the selected address SA. In addition, the memory control unit 522 updates the output of the temporary storage unit 44 belonging to the selected group SG by outputting the update instruction acq specifying the selected group SG to the temporary storage unit 44.

  Each function of the signal processing unit 5 is realized by an electronic circuit which is hardware. The electronic circuit may be realized by a digital circuit, an analog circuit, or a combination thereof. Also, some of these functions may be realized by processing executed by the CPU.

[1-2. Operation]
Here, the overall operation of the histogram generation unit 52 will be described along the state machine diagram of FIG. The histogram generation unit 52 has an IDLE state, a SET state, a READ state, a SUM state, and a WRITE state, transitions these states as appropriate, and executes an operation according to each state. However, depending on the situation, the SUM state and the SET state, and the WRITE state and the READ state can coexist. Further, in the drawing, emp means that data does not exist in any of the plurality of temporary storage units 44 (hereinafter, read register group), and din means that data exists in the read register group.

  The histogram generation unit 52 is reset each time the information generation unit 51 executes an information generation process using a histogram. When the signal processing unit 5 is reset, the IDLE state is established. At this time, the histogram stored in the histogram storage unit 6 is also reset.

  The IDLE state is a state waiting for data to be written to the read register group. When data is written to the read register group in the IDLE state, the read register group becomes din, and the histogram generation unit 52 transitions to the SET state.

  In the SET state, the comparing unit 521 operates to output the selected group SG, the selected address SA, and the selected data SD to the memory control unit 522. Thereafter, the histogram generation unit 52 transitions to the READ state.

  In the READ state, the memory control unit 522 reads data of the selected address SA from the histogram storage unit 6. At this time, if the read register group is emp, the histogram generation unit 52 transitions to the SUM state.

  In the SUM state, the memory control unit 522 generates an integrated value obtained by adding selected data to data read in the READ state. Thereafter, the histogram generation unit 52 transitions to the WRITE state.

  In the WRITE state, the memory control unit 522 writes the integrated value generated in the SUM state to the selected address SA of the histogram storage unit 6, and outputs the update instruction acq specifying the selected group SG to the read register group. If the read register group is emp as a result of updating the status of the read register group by the update instruction acq, the histogram generation unit 52 transitions to the IDLE state. On the other hand, if the read register group is din, the histogram generation unit 52 transitions to the SET state.

If the read register group is din in the previous READ state, the histogram generation unit 52 transitions to the SUM + SET state.
In the SUM + SET state, the operation in the SUM state by the memory control unit 522 and the operation in the SET state by the comparison unit 521 are executed in parallel. Thereafter, the histogram generation unit 52 transitions to the WRITE + READ state.

  In the WRITE + READ state, the operation in the WRITE state and the operation in the READ state by the memory control unit 522 are executed in parallel. Thereafter, the histogram generation unit 52 transitions to the SUM + SET state if the state of the read register group is din, and transitions to the SUM state if the state of the read register group is emp.

[1-3. effect]
According to the first embodiment described above, the following effects can be obtained.
(1a) In the laser radar 1, a large number of photodetectors 31 constituting one pixel are divided into a plurality of light receiving groups G1 to Gx, and distributed to a plurality of measuring units 4 provided for each of the light receiving groups G1 to Gx. Processing of the pulse signal P is executed, and the processing results are integrated to generate a histogram. Therefore, according to the laser radar 1, it is possible to reduce the processing load of the individual measurement units 4 without reducing the sensitivity of the light detector 31, that is, without reducing the detection performance. That is, in the conventional apparatus including one measurement unit in one pixel, the measurement unit needs to execute processing for all pulse signals shown in a graph obtained by adding all the graphs in FIG. On the other hand, in the laser radar 1 having a plurality of measurement units 4 in one pixel, each measurement unit 4 executes processing only on the pulse signal shown in any one of the graphs in FIG. Processing load is reduced.

  (1b) In the laser radar 1, the measurement unit 4 is provided with a temporary storage unit 44 that stores time information Tp and light amount information Cp which are measurement results. Therefore, the signal processing unit 5 does not have to process in real time at the generation timing of the pulse signal P, and can execute processing using the time until the next light emission, so that the measurement result is used without omission Can.

[2. Second embodiment]
[2-1. Differences from the First Embodiment]
The basic configuration of the second embodiment is the same as that of the first embodiment, so the difference will be described below. The same reference numerals as those in the first embodiment denote the same components, and reference is made to the preceding description.

  In the first embodiment described above, the light receiving groups G <b> 1 to Gx and the plurality of measurement units 4 are in one-to-one correspondence. On the other hand, the second embodiment is different from the first embodiment in that the correspondence between the two can be appropriately changed.

  As shown in FIG. 6, the laser radar 1a of the present embodiment includes a connection unit 7 and a connection control unit 8 in addition to the configuration of the laser radar 1 of the first embodiment. However, the number of measurement units 4 is set to the number x or less of the light reception groups G1 to Gx. The following description is given assuming that the number of measurement units 4 is two. The connection unit 7 corresponds to the front connection unit, and the connection control unit 8 corresponds to the front control unit.

  The connection unit 7 assigns the light reception groups G1 to Gx to each of the two measurement units 4 in accordance with the instruction from the connection control unit 8. That is, one pixel is divided into upper and lower two areas, the first measurement unit 4 processes the pulse signal P from the light reception group belonging to the upper area, and the second measurement unit 4 from the light reception group belonging to the lower area Process the pulse signal P of That is, the connection unit 7 appropriately changes the formation of the light reception group which causes each measurement unit 4 to take charge of processing.

  The connection control unit 8 acquires situation information indicating the situation in which the laser radar 1a is used, and changes the setting of the connection unit 7, that is, the boundary between the upper area and the lower area of the pixel according to the acquired situation information. .

  Here, the connection control unit 8 acquires information as a status information from a sensor or the like that monitors the intensity of disturbance light incident on the light receiving array unit 3. Then, as shown in the upper column of FIG. 7, the connection control unit 8 reduces the number m of light receiving groups belonging to the upper region according to the situation information, and the number n of light receiving groups belonging to the lower region May be increased.

  That is, when the disturbance light is strong, the brightness of the object to be measured tends to be a gradation that changes from bright to dark from top to bottom. By reducing the number of SPADs in the upper region where strong disturbance light is incident, the load on the measurement unit 4 that processes the upper region is reduced. Note that this vertical relationship may be reversed by the lens.

  Further, the connection control unit 8 may obtain information as a condition information from a sensor or the like that monitors the condition of the road surface. In this case, when the connection control unit 8 detects that the road is a snowy road from the status information, as shown in the lower column of FIG. 7, the connection control unit 8 increases the number m of light receiving groups belonging to the upper area and belongs to the lower area. The number n of light receiving groups may be reduced.

  That is, on a snowy road, the road surface reflection becomes strong, so the brightness of the object to be measured tends to be a gradation that changes from dark to bright from top to bottom. By reducing the number of SPADs in the lower area where the road surface reflection is strong, the load on the measurement unit 4 that processes the lower area is reduced. Note that this vertical relationship may be reversed by the lens.

[2-2. effect]
According to the second embodiment described above, the effects (1a) and (1b) of the first embodiment described above are exhibited, and further, the following effects are exhibited.

  (2a) According to the laser radar 1a, since the number of light receiving groups allocated to each measurement unit 4 is changed according to the situation, the load on each measurement unit 4 can be further suppressed from becoming excessive. .

[3. Third embodiment]
[3-1. Differences from the First Embodiment]
The basic configuration of the third embodiment is the same as that of the first embodiment, so the difference will be described below. The same reference numerals as those in the first embodiment denote the same components, and reference is made to the preceding description.

  In the first embodiment described above, the measurement results of the plurality of measurement units 4 are processed by one signal processing unit 5. On the other hand, the third embodiment is different from the first embodiment in that it has a plurality of signal processing units 5 and that the correspondence with the measurement unit 4 can be appropriately changed.

  As shown in FIG. 8, in addition to the configuration of the laser radar 1 of the first embodiment, the laser radar 1 b of the present embodiment includes a connection unit 9 and a connection control unit 10. The laser radar 1 b also includes two signal processing units 5 and two histogram storage units 6. The number of signal processing units 5 and histogram storage units 6 may be three or more. The connection unit 9 corresponds to a post connection unit, and the connection control unit 10 corresponds to a post control unit.

  The connection unit 9 assigns the measurement unit 4 and, consequently, the light reception groups G1 to Gx to the two signal processing units 5 in accordance with the instruction from the connection control unit 10. That is, one pixel is divided into upper and lower two regions, and the first signal processing unit 5 creates a histogram based on the measurement results of the plurality of measuring units 4 that process the pulse signal P from the light receiving group belonging to the upper region. Do. In addition, the second signal processing unit 5 creates a histogram based on the measurement results of the plurality of measurement units 4 that process the pulse signal P from the light reception group belonging to the lower region.

  The connection control unit 10 acquires situation information indicating the situation in which the laser radar 1 b is used, and changes the setting of the connection unit 9, that is, the boundary between the upper area and the lower area of the pixel according to the acquired situation information. .

  Here, the connection control unit 10 acquires information as a situation information from a sensor or the like that monitors the attitude of the vehicle. In the present embodiment, the laser radar 1b is set to emit a laser beam toward the road surface. Then, basically, as shown in FIG. 9, the connection control unit 10 sets the number m of light receiving groups belonging to the upper region to a large number, and sets the number n of light receiving groups belonging to the lower region to a small number. According to, change the ratio of m, n.

  That is, when the laser beam is emitted toward the road surface, the reflected wave from a greater distance is detected in the upper area, and the reflected wave from a closer area is detected in the lower area. Note that this vertical relationship may be reversed by the lens. By increasing the number m of light receiving groups assigned to the upper region, it becomes possible to detect a weak signal from a long distance, although the resolution becomes coarse. Also, by reducing the number n of light receiving groups allocated to the lower region, it is possible to improve resolution instead of sacrificing detection of weak signals. Further, the distance from the attitude of the vehicle to the road surface reached by the laser beam may be estimated for each light receiving group, and the ratio of m and n may be changed according to the estimated distance.

[3-2. effect]
According to the third embodiment described above, the effects (1a) and (1b) of the first embodiment described above are exhibited, and further, the following effects are exhibited.

(3a) According to the laser radar 1b, the size of the area for generating the histogram and hence the detection accuracy can be appropriately changed according to the situation.
[4. Fourth embodiment]
[4-1. Differences from the First Embodiment]
The basic configuration of the fourth embodiment is the same as that of the first embodiment, so the difference will be described below. The same reference numerals as those in the first embodiment denote the same components, and reference is made to the preceding description.

  In the first embodiment described above, the trigger signal TG is generated, and the histogram is updated using only the light amount information Cp obtained at the timing of the trigger signal TG. On the other hand, the fourth embodiment is different from the first embodiment in that the light amount information Cp is repeatedly generated in synchronization with the clock and the histogram is updated using all the light amount information Cp.

The laser radar 1c of the present embodiment, as shown in FIG. 11, includes an irradiation unit 2, a light receiving array unit 3c, a plurality of measurement units 4c, a signal processing unit 5, and a histogram storage unit 6.
The light receiving array unit 3c has a plurality of light receiving groups G1 to Gx. Each light receiving group Gi has Mi photodetectors 31c. Each of M1 + M2 +... + Mx light detectors 31c has an SPAD, and these SPADs are arranged to form a two-dimensional matrix, and form a light receiving surface, as in the first embodiment.

  As shown in FIG. 12, each photodetector 31 c includes a SPAD 81, a quench resistor 82, an inverting circuit 83, and a DFF circuit 84. That is, compared with the photodetector 31 of the first embodiment, in the photodetector 31c, the delay circuit 85 is omitted and the connection state of the DFF circuit 84 is different.

  The DFF circuit 84 latches the output of the inverting circuit 83 at the timing of the rising edge of the clock CK, and outputs this as a pulse signal P. Also, the output of the DFF circuit 84 is reset by the reset signal RS.

  That is, when photons are incident on the SPAD 81, the photodetector 31c outputs a pulse signal P in response to this. At this time, the pulse width of the pulse signal Pr output from the inverting circuit 83 continues until the Geiger discharge of the SPAD 81 stops due to the voltage drop generated by the current flowing through the quench resistor 82. The pulse signal Pr is converted by the DFF circuit 84 into a pulse signal P synchronized with the clock CK. That is, the pulse width of the pulse signal P output from the DFF circuit 84 includes a shift by a quantization error due to the clock CK.

Returning to FIG. 11, the measuring unit 4c includes a clock unit 42c, a counting unit 43c, and a temporary storage unit 44c.
The clock unit 42c has a synchronous counter that operates according to the clock CK. The timer unit 42c starts counting at the irradiation timing notified from the irradiation unit 2 and continues the counting operation at least for the time required for the light signal to reciprocate at the maximum detection distance. Then, the timer unit 42c outputs the count value of the synchronous counter as time information Tp. That is, the time information Tp changes in synchronization with the clock CK, and represents an elapsed time from the irradiation timing.

Counting unit 43c is a response number Cx from the photodetector 31c is the number of pulse signals _P 1 _{to P Mi} outputted simultaneously determined at all times by using an encoder or the like. Furthermore, the count unit 43c repeatedly calculates the adjustment response number, which is the result of subtracting the bias value Cb from the response number Cx, for each timing of the clock CK, that is, each time the time information Tp changes. The light amount information Cp indicating the luminance of the light signal is output. That is, similarly to the time information Tp, the light amount information Cp changes in synchronization with the clock CK.

  The temporary storage unit 44c is the same as the temporary storage unit 44 except that the light amount information Cp is stored at the timing of the clock CK instead of the trigger signal TG. Thereby, the light amount information Cp is stored in all the time bins identified by the time information Tp in the temporary storage unit 44c.

[4-2. effect]
According to the fourth embodiment described above, the effects (1a) and (1b) of the first embodiment described above are exhibited, and further, the following effects are exhibited.

  (4a) According to the laser radar 1c, since the time information Tp and the light amount information Cp are always generated at timing synchronized with the clock CK, there is no need to generate the trigger signal TG, and the trigger unit 41 can be omitted. Configuration can be simplified.

[5. Other embodiments]
As mentioned above, although embodiment of this indication was described, this indication can be variously deformed and implemented, without being limited to the above-mentioned embodiment.

  (5a) In the above embodiment, among the two-dimensional matrix of SPAD, the light receiving group is configured in units of rows, but the present disclosure is not limited to this. For example, in the two-dimensional matrix of SPAD, the light receiving group may be configured in units of columns or may be configured in units of chunks of arbitrary shape.

  (5b) In the second embodiment, the connection unit 7 switches connection on a light reception group basis, but the present disclosure is not limited to this. For example, the connection unit 7 may be configured to switch the connection in units of individual photodetectors 31.

  (5c) In the second embodiment, the connection control unit 8 changes the boundary between the upper area and the lower area of the pixel based on the status information, but the present disclosure is not limited to this. Absent. The target of the change based on the status information may include, for example, at least one of the number of photodetectors forming the light reception group, the size of the pixel formed by the light reception group, and the shape of the pixel.

  (5d) In the third embodiment, the plurality of signal processing units 5 respectively process partial regions in one pixel and generate a plurality of histograms for one pixel, but the present disclosure is limited to this. It is not a thing. For example, the plurality of signal processing units 5 respectively generate a histogram for one pixel, and the connection unit 9 switches the light reception groups G1 to Gx to be associated with each pixel so that the size of each pixel and each pixel The configuration may be configured to appropriately change at least one of the shape and the number of photodetectors included in each pixel.

  (5e) In the third embodiment, the connection control unit 10 sets each region or the like as a region in the pixel corresponding to each of the signal processing units 5 or a pixel corresponding to each of the signal processing units 5 as a region or the like. The connection by the connection unit 9 may be changed so that the number of the photodetectors 31 forming the or the size of each region or the shape of each region is the same. In addition, the connection control unit 10 is connected by the connection unit 9 so that the number of photodetectors 31 forming each region or the like, or the size of each region or at least one of the shapes of each region differs depending on the pixel. May be configured to change.

  (5f) In the second and third embodiments, the number of connections is changed based on the status information acquired by the connection control units 8 and 10. However, the present disclosure is not limited to this. For example, the number of connections may be set in advance based on the characteristics (for example, angle of view, distortion, etc.) of the light receiving lens and the light irradiation range of the irradiation unit 2.

  (5g) In the second and third embodiments, the intensity of disturbance light, the road surface condition, and the posture of the vehicle are used as status information acquired by the connection control unit 8 or 10, but the present disclosure is limited thereto It is not something to be done. For example, various pieces of information having a correlation with disturbance light, such as time or weather, may be used as the situation information. In addition, as the status information, various information such as a map showing the acceleration of the vehicle or the inclination angle of the road may be used. Furthermore, past situation information etc. may be used as situation information.

(5h) In the second and third embodiments, although the connection parts 7 and 9 are provided on either the input side or the output side of the plurality of measurement parts 4, the connection parts 7 and 9 are provided simultaneously. It is also good.
(5i) In the above embodiment, the RAM used as the temporary storage unit 44 has an address associated with the time information Tp, but the present disclosure is not limited to this. For example, the RAM used as the temporary storage unit 44 may store the time information Tp and the light amount information Cp in association with each other as data. According to this, since the RAM used as the temporary storage unit 44 does not need to prepare an address for all time bins, the capacity of the RAM is reduced particularly when the pulse signal frequency from the light receiving group is low. be able to. Further, in this case, the histogram generation unit 52 may be configured to compare the time information Tp itself instead of comparing the addresses.

  (5j) In the laser radar 1c according to the fourth embodiment, the light receiving array 3 and the measuring unit 4 in the laser radar 1 according to the first embodiment are replaced with the light receiving array 3c and the measuring unit 4c. The present disclosure is not limited to this. For example, as in a laser radar 1d shown in FIG. 13, even if the light receiving array unit 3 and the measuring unit 4 of the laser radar 1a of the second embodiment are replaced with a light receiving array unit 3c and a measuring unit 4c. Good. In addition, as in the laser radar 1e shown in FIG. 14, even if the light receiving array unit 3 and the measuring unit 4 of the laser radar 1b according to the third embodiment are replaced with the light receiving array unit 3c and the measuring unit 4c. Good.

  (5k) The plurality of functions of one component in the above embodiment may be realized by a plurality of components, or one function of one component may be realized by a plurality of components . Also, a plurality of functions possessed by a plurality of components may be realized by one component, or one function realized by a plurality of components may be realized by one component. In addition, part of the configuration of the above embodiment may be omitted. In addition, at least a part of the configuration of the above-described embodiment may be added to or replaced with the configuration of the other above-described embodiment. In addition, all the aspects contained in the technical thought specified from the wording described in the claim are an embodiment of this indication.

  (5l) The present disclosure can be realized in various forms such as a system including the light measurement device as a component, a measurement method of an optical signal, and the like in addition to the light measurement device described above.

1, 1a to 1e: laser radar, 3, 3c: light receiving array unit, 4, 4c: measuring unit, 5: signal processing unit, 31, 31c: photodetector.

Claims (20)

A plurality of light detectors (31, 31c) outputting pulse signals by incidence of photons form a light receiving group, and the plurality of light receiving groups are configured to form one pixel, and the light receiving including one or more of the pixels An array unit (3, 3c),
One or more of time information provided for each of the plurality of light receiving groups, time information indicating an elapsed time from an irradiation timing input from the outside according to the pulse signal output from the light receiving group, and the time information Measuring units (4, 4c) configured to generate light amount information acquired at each of the timings of
A signal processing unit (5) configured to obtain a flight time of light according to at least one of the time information or the light amount information measured by the plurality of measurement units corresponding to the one pixel;
Equipped with
An optical measurement device using, as the light amount information, the number of light detectors outputting the pulse signal among a plurality of light detectors belonging to the light reception group. The optical measurement device according to claim 1, wherein
A plurality of the signal processing units,
A post connection unit (9) configured to connect each of the plurality of measurement units to any of the plurality of signal processing units;
A post control unit (10) configured to change a region in a pixel in charge of processing by the plurality of signal processing units by changing connection by the post connection unit;
An optical measurement device further comprising The optical measurement device according to claim 2, wherein
The postfix control unit is configured to obtain status information indicating a status in which the light measurement device is used, and to change connection in the postfix connection unit according to the obtained status information.
Optical measurement device. The optical measurement device according to claim 3, wherein
The postfix control unit estimates the distance from the status information to the measurement target, and changes the number of connections of the measurement units to each of the plurality of signal processing units based on the estimated distance to the measurement target. Configured as
Optical measurement device. The optical measurement device according to any one of claims 1 to 4, wherein
A front-end connection unit (7) configured to connect each of the plurality of light detectors included in the one pixel to any of the plurality of measurement units;
A front control unit (8) configured to change the formation of the light reception group by changing the connection by the front connection portion;
An optical measurement device further comprising A plurality of light detectors (31, 31c) outputting pulse signals by incidence of photons form a light receiving group, and the plurality of light receiving groups are configured to form one pixel, and the light receiving including one or more of the pixels An array unit (3, 3c),
One of information provided for each of the plurality of light reception groups, time information representing an elapsed time from an irradiation timing externally input according to the pulse signal output from the light reception group, and the time information Measuring units (4, 4c) configured to generate light amount information acquired at each of the above timings;
A plurality of signal processing units (5) configured to calculate a flight time of light according to at least one of the time information and the light amount information measured by the plurality of measurement units;
A post connection unit (9) configured to connect each of the plurality of measurement units corresponding to the plurality of pixels to any one of the plurality of signal processing units;
At least one of the number of light detectors corresponding to each of the signal processing units or the size or shape of a pixel corresponding to each of the signal processing units by changing the connection by the rear connection unit. A post-control unit (10) configured to change one
Equipped with
An optical measurement device using, as the light amount information, the number of light detectors outputting the pulse signal among a plurality of light detectors belonging to the light reception group. The optical measurement device according to claim 6, wherein
The post-position control unit performs the post-connection such that the number of light detectors forming each pixel corresponding to each of the signal processing units, or the size of each pixel or the shape of each pixel is the same. Configured to change the connection by
Optical measurement device. The optical measurement device according to claim 6, wherein
The post control unit may change the number of light detectors forming each pixel corresponding to each of the signal processing units, or at least one of the size of each pixel or the shape of each pixel, depending on the pixel. Configured to change the connection by said post connection,
Optical measurement device. The optical measurement device according to any one of claims 6 to 8, wherein
The postfix control unit is configured to obtain status information indicating a status in which the light measurement device is used, and to change connection in the postfix connection unit according to the obtained status information.
Optical measurement device. The optical measurement device according to claim 9, wherein
The postfix control unit estimates the distance from the status information to the measurement target, and changes the number of connections of the measurement units to each of the plurality of signal processing units based on the estimated distance to the measurement target. Configured as
Optical measurement device. The optical measurement device according to any one of claims 6 to 10, wherein
A pre-connection unit (7) configured to connect each of the plurality of light detectors included in the light receiving array unit to any of the plurality of measurement units;
A front control unit (8) configured to change the formation of the light reception group by changing the connection by the front connection portion;
An optical measurement device further comprising The optical measurement device according to claim 5 or 11, wherein
The front control unit is configured to obtain status information indicating a status in which the light measurement device is used, and to change a connection in the front connection according to the obtained status information.
Optical measurement device. The optical measurement device according to claim 12, wherein
The front-end control unit estimates the tendency of brightness of the object to be measured from the situation information, and forms the number of photodetectors forming the light reception group based on the tendency of the brightness or the light reception group Configured to change at least one of the size or shape of the pixels being
Optical measurement device. The optical measurement device according to any one of claims 1 to 13, wherein
The signal processing unit generates a histogram by integrating values indicated by the light amount information for each time indicated by the time information according to the time information and the light amount information measured by the plurality of measurement units. Configured histogram generator (52),
Light measuring device comprising: The optical measurement device according to claim 14, wherein
Each of the plurality of measurement units includes a temporary storage unit (44, 44c) configured to store the generated light amount information and the time information.
The histogram generation unit is configured to generate the histogram in accordance with information stored in the temporary storage unit provided in each of the plurality of measurement units.
Optical measurement device. The optical measurement device according to claim 15, wherein
The histogram generation unit
The time information stored in the temporary storage unit provided in each of the plurality of measurement units is compared, and the time information and the time information are associated in order from the smallest value of the time information. A comparison unit (521) configured to read out the light amount information;
A memory control unit (522) configured to update the contents of a memory storing the histogram according to the time information and the light amount information read by the comparison unit;
Light measuring device comprising: The optical measurement device according to claim 16, wherein
The comparison unit is configured to supply the result of the addition of the plurality of light amount information to the memory control unit when the plurality of light amount information having the same time information are read from different temporary storage units. Was done
Optical measurement device. The optical measurement device according to any one of claims 15 to 17, wherein
The temporary storage unit is configured to store the light amount information at an address associated with the time information.
Optical measurement device. The optical measurement device according to any one of claims 1 to 18, wherein
The measuring unit (4c)
A timer unit (42 c) configured to output, as the time information, a count value obtained by counting an elapsed time from the irradiation timing according to a clock;
A count unit (43c) configured to generate the light amount information each time the time information changes;
Light measuring device comprising: The optical measurement device according to any one of claims 1 to 18, wherein
The measurement unit (4)
A trigger unit configured to output a trigger signal representing a light reception timing of an optical signal incident on the light reception group when the number of pulse signals simultaneously output from the light reception group is equal to or greater than a trigger threshold ( 41),
A timer (42) configured to output a time from the irradiation timing to the light reception timing as the time information;
A count unit (43) configured to generate the light amount information each time the trigger signal is output;
Light measuring device comprising:

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